UV LED technology
The usage of the AlGaN-LED technology means that spectral ranges from 360 nm to 230 nm can be covered completely. In order to increase the lifetime of the sensitive UV-LEDs a special control electronics (smartPOWER) was developed with which the expected life-span could be extended by the factor > 10. Under these operating conditions, the lifetimes of the sensitive UV radiation sources have risen to > 2 years for the first time. This is an important prerequisite for the usage in continuously operating gas measuring systems. Furthermore, the UV LED can be modulated with almost any desired frequencies so that rapid changes in the gas concentration can also be captured. Response times of t90% <100 milliseconds can therefore be achieved easily.
The physical structure consists of a photometer with two silicon reception detectors. The reference detector continuously monitors the radiation intensity of the UV LED and this serves to compensate aging effects and temperature influences. The measuring detector detects the selective radiation absorption in a 100-mm-long measuring cuvette, which is provided with a special coating on the inside in order to suppress disturbing hang-up effects. The control of the UV LED and the evaluation of the detector signals are carried out in a powerful microprocessor electronics, which is located below the photometer.
The LEDs required for the different gas measurements are selected by a spectral analysis and then assigned to the respective measurement task. As a result of this measure, the usage of optical filters for the spectral restriction to the particular type of gas becomes obsolete.